Acid-base

Question 1

What is type I renal tubular acidosis? What is the key diagnostic feature?

Answer 1

this is a DISTAL defect with impaired proton secretion that causes secondary hyperaldosteronism. Because there is poor proton secretion, the urine pH is >5.3. Too much aldosterone = low potassium

Question 2

What are some causes of type I renal tubular acidosis?

Answer 2

-autoimmune disease, drugs, infection, cirrhosis, SLE, obstruction, nephrocalcinosis (may see stones on imaging)

Question 3

How is type I renal tubular acidosis treated?

Answer 3

-give oral bicarb, potassium, and a thiazide diuretic (reduces Ca in urine)

Question 4

What is type II renal tubular acidosis? What is the key diagnostic feature?

Answer 4

• A proximal defect of HCO3- resorption

- Urine pH is

Question 5

What are the causes of type II renal tubular acidosis?

Answer 5

• idiopathic, multiple myeloma, fanconi syndrome, wilson disease, amyloidosis, vitamin D deficiency, autoimmunity
• May see bone lesions

Question 6

What are treatments for type II RTA?

Answer 6

bicarb, K, thiazide or loop diuretic

Question 7

What is type 4 RTA? What are key tests?

Answer 7

due to primary or secondary hyperaldosterone

-urine pH

Question 8

What are the causes of type 4 RTAs?

Answer 8

-primary renin or aldo deficiency, DM, Addison disease, sickle cell

Question 9

What is the treatment for type 4 RTA?

Answer 9

fludrocortisone, K restriction

Question 10

What is one strategy for determining acid-base disturbances?

Answer 10

1. Is it acidosis or alkalosis?
2. Is it primary respiratory or metabolic?
3. Is it compensated or not (if not, you also have a disturbance in the other system):
   -Winter’s formula gives anticipated CO2 for acidosis
   CO2 = 1.5bicarb + 8 plus or minus 2
   -To get anticipated CO2 for alkalosis:
   -0.9bicarb + 16 plus or minus 2
   Metabolic compensation for respiratory derangements depend on whether they are acute or chronic:
   -acute resp acidosis: 1 for every 10 mmHg change
   -chronic resp acidosis: 3.5 for every 10 mmHg change
   -acute resp alkalosis: 2 for every 10 mmHg change
   -chronic resp alkalosis: 4 for every 10 mmHg change
4. If metabolic acidosis: is it anion gap or non anion gap?
5. If anion gap acidosis, determine if there is a gap-of-the-gap:
   change in the anion gap over the change in the bicarb
   -If the gap is 1 to 2, you just have an anion gap acidosis
   -If the gap is less than 1, you have a normal anion gap AND a high anion gap metabolic acidosis
6. If you have a normal anion gap acidosis of unknown cause, calculate the urine anion gap (urine Na +urine K - urine Cl). If it is negative, suspect RTA, if it is normal (ie. zero or positive) suspect loss through the gut.